Automatic telephone system



C. E. LOMAX ATOMATIC TELEPHONE SYSTEM Ango 219 E928@ msu/'03 C. E. LOMXAUTOMATIC TELEPHONE SYSTEM Patented Aug. `21, 1928.

UNITED STATES.k PATENT OFFICE.

CLARENCE E. LOMAX, OE eIIICAGO, ILLINOIS, AssIGNOR, BY MEsNEASSIGNMENTS, To

AUTOMATIC ELECTRIC INC., OE CHICAGO, ILLINOIS, A CORPORATION or DELA-WARE.

4Application filed May 9,

This invention relates in general to automatic telephone systems, butmorer particularly to small private installations, and its principalobject iste provide a common talking, selective signaling system whichis anv improvement over the one described in Patent No. 1,665,466,issued to Middleton on April 10, 1928. rMore specifically, the principalobject of the invention is to provide an eticient, yet inexpensivesystem for private installations, comprising a common talking line witha plurality otsubstations thereon, a connector switch to furnishindividual or selective signaling, anormally inoperative power planthavingy a dry-cell starting bat tery and motor generator' carrying setto 'furnish the necessary switching and talking current, a vibrator''controlled impedance coil to 'furnish signaling current, and a codeVcall machine to sound any one of ten dilicrent codes twice and then beauton'iatically cut off. Another object of the invention is to provide anew and improved direct line system, comprising two individual lines,vand a relay group vto control the signaling and talking circuits. Thissystem is used in conjunction with the above describedcommon talking,seleotivesignaling system to relieve it, and has access to the sainepower plant.

The means by which the 'foregoing and other objects Vare accomplishedwill be fully set forth hereinafter, reference being made to theaccompanying drawings, of which Fig. 1 is a circuit diagram of twosubscribers telephones A and E on the common line, connector H, and codecall machine CCywhile Fig. 2 is a Circuit diagram or' the subscriberstelephones A and E on the direct. line, relay group R, and power plantequipment l).

Referring to Fig'. 1, the telephones A and Il are of the usualautmnatic4 type and are con nected in bridge ot' a singlepair of talkingconductors.

The common line conductors oi the substations are connected to the linerelay oil the connector, which is mechanically ot vthe well` knownvertical and rotary type oif switch and has its bank contacts arrangedin horizontal rows or levels.` (All the contacts in the bank are adaptedto be enga-ged by the wiper 71. The contacts, such as 72, in one ofthe'lower levels of the bank are connected to the individual signalingconductors, such as (S5, ein tending to the several sub-stations, suchas E,

AUTOMATIC TELEPHONE SYSTEM.

1925. Serial No. 29,001.

nine levels. The contacts, such 'as 73, in the upper or tenth level ofthe bank are connected to conductors, such as v74, extendingto one setof bank cont-acts of the code call machine CC. e

The code call machine CC Consists, essentially, of two sets of banks andassociated wipers 86 and 87, a plurality,ofrelays anda mo tor magnet S5for controlling and stepping' same, and a double coil magnet 84 forcontrolling thecircuits of the code callbells, such as 98 and 99. Themachine is mechanically oll the rotary type of switch of which thewipers have a home position and move i n a :forward direction only. Thecontacts ot one bank are grounded; while the contacts ol the other bankare connected in pairs to the bank so as to-produce tencodes,.represented by the ten contacts, ysound any code twice, and thenautomatically be cut oli'.

Referring to Fig. 2, the telephones A and E are of the usual manual typeand are lo- .cated at the same places as the automatic telelpullsupstarting'relay 32, Fig. 1, when a receiver is removed, which startsthe motor-r generator set. The generator builds up to a current output,beyond that ot the dry cells, is connected in parallel therewith byrelay 14:1, and thus carries' the entire switchboard load and alsoserves to reverse the currentr through the dry-cells and prolong theirlife. Relay 11i-1 serves as a circuit breaker when the generator' diesdown, after `all receivers are replaced. Substation ringii'ig currentconsists ot a series of discharge kicks from theimpedanee coil 143 whichis controlled by the vibrator 142. y

lVhile separate ground connections and batteries, such as groundedcontact 39 of line relay of connector Hand. grounded {battery oit' saidrelay, are shown for convenience contacts in the upper level ot theconnector GEN. of the power equipment P. The battery feed conductors 143and 149 are shown leading to the negative and positive bus bars,respectively, of the switchboard to supply the current therefor.

The utility of a telephone system of the above nature obtains, forexample, in the case of a school where there are a large number ofsubscribers having a very low calling rate. The subscribers can haveeconomical and efficient inter-communica ting telephone service withindividual and code call signaling. In the case of two subscribers, suchas the principal and his assistant, having occasion to converse witheach other frequently, a direct line is extended between the subscriberswherebythey can signal and converse by using the same power equipmentwithout tying up the commen talking line. T hey are provided withseparate telephones or, if found more desirable, one telephone could beused having separate bells and a switch for switching from one line tothe other. s Y

Having given a brief description of the apparatus, the operation of samewill nowbe explained more in detail. For this purpose it will be assumedthat the subscriber at station A desires to call the subscriber atstation E, on the common talking line, and that the latter line is idle.In order to dothis, the subscriber at station A removes his receiver anddia-ls the number of station E. f lllhen the receiver is removed atsubstation A, line relay 23 energizes over a circuit from groun l,armature 57 and its resting contact, lower winding of line relay 23,line conductor 21, substation A with the receiver, transmitter, andcalling device in bridge of the line, line conductor 22, upper windingof line relay 23 to battery. Upon energizing, line relay 23 closes acircuit for slow to release relay 24 at armature 39, which circuit maybe traced from ground, armature 54 and its resting contact, releaserelay 24, armature 39 and its working contact, and vertical magnot 33 tobattery. Vertical magnet 33 is not energized at this time on account ofthe high resistance of release relay 24. Release relay 24, uponenergizing, opens a point in the circuit of release magnet 35 atarmature 42; prepares a circuit for slow to release relay 25 inserieswith vertical magnet 33 at armature 41; and closes a circuit forstarting relay 32 at armature 40, which relay-energizes to close acircuit for the busy lamp L and start the motor-generator set inoperation to supply carrying current for the switch-board, as will beexplained hereinafter.

lllhen the calling subscriber operates his calling device for the firstdigit in the desired number, which it will be assumed is 2 in thepresent instance, line relay 23 deenergizes a corresponding number oftimes. Each time armature 39 of line relay 23 breaks away from itsworking Contact, the initial circuit of release relay 24 is opened.Release relay 24, however, (toes not deenergize at this time but ismaintained energized over a circuit which, before the olf normal springshave shifted, is as follows: ground, armature 54 and its restingContact, release relay 24, armature 41 and its working` Contact,normally closed contact and olf normal spring 37, series relay 25, andvertical magnet 33 to battery. Series relay 25, however, does notenergize in series'with relay 24 on accountof the high resistance of thelatter. Each time armature 39 comes into engage-V ment with its restingcontact, it short circuits release relay 24, whereupon vertical magnetand relay 25 energize in series, re-

lease relay 24, being` maintained energizedl during this time by itsshort circuitcd winding which makes it slow acting. Each time armature39 is attracted, the shunt is removed from release relay 24 as soon asarmature 39 breaks away from its resting contac and vertical magnet 33immediately deenergizcs. Series relay 25, however, receives some currentin series with relay 24 which as sists in holding it up, the actionbeingeX- plained in Patent No. 1,671,7 91, issued May 29, 1928, to R. E.Ste-lilik, Each time armaturc 39 comes into engagement with its workingcontact, series rela-y 25 is short circuited. It is held up for aninterval, however, by its short circuited winding and, consequently,remains energized throughout the series of deenergizations of linerelayl 23. By the oper ation ofvertical magnet 33, the switch wiper 71is raised opposite the second level of bank contacts. Series relay 25,upon energizing, serves to maintain `its owircircuit and that ofvertical magnet 33 intact at armature 43 after the olf normal springshave shifted, as they do upon the first vertical step. At the end of thevertical movement, line relay 23 comes to rest in an energized conditionand series relay 25, being short circuited, deenergizes after an instantand at armature 43 shifts the. operating circuit from the vertical tothe rotary magnet.

.The calling subscriber now operates his callii'ig device in laccordancewith the second and last digit in the desired number, which, it will beassumed. is 5 in the present instance, whereupon `the line relay23'deenergizes a corresponding number of times. Each time armature 39breaks away from its working contact and before it comes into engagementwith its resting Contact, release relay 24 is held up over the followingcircuit: ground, armature 54 and its restino contact, relay 24, armature41 and its working Contact, normally open contacts controlled by offnormal .ricain-eea@ spring-3'?, armature `43 and its` resting contact,relay 2G, and rrotary'l magnet'34 to'battery. Rotary magnet 34 andr'elaly 26 howv ever, are `not energized at this timev on account ot'the high resistance ofvfrelay' 24'. When armature 39 eomesfintoengagement with Vits resting contact,relayf24 is short circuited,whereupon rotary m`agnetf'34 energizes. Also, relay 26 ei'iergizesinseries with* rotarymagnet 34. Each time armature 39 breaks away fromits resting contact rotary magnet 34 deenergizes. Relay 26, however,

being slow to release remains-energized in series with rotary magnet 34and retains its armature attracted4 throughout the rotary ."iovement. Bythe operation of rotary, magnet 34, the wiper Klis rotated-step bystepinto engagement with i the Contact .,72`wh1ch is connected with thesignaling conductor of` the operation ot which willbe explainedvhereinafter.

At the end oft' the rotary movement, the

relay 26 deenergizes and closes the circuit for relays 29 and 31 atarmature 44; and closes the signaling circuit for the called substationE at armature 45'.' The bell at the called substation is rung -byaseries of discharge kicks from an impedance coil (to be explained herefinatter) over the,` signaling circuit which may be traced frombatteryby'way of' impedance coil 143`and its bridged condenser,conductorv 67, resting contact and armature 51j, resting contact andarmaturev45, arn'iature't rand its resting contact, conductor 70, wiper71, bank contact 7 2, conductor 65, bell and -condenser of substation E,line conductor 21,to working contact and grounded armature 57, whicharmature is now inattracted position due to relay 31'havingenergized;yThe signaling circuit is completed to direct ground instead of throughthe lowerwinding ofv line relay 23 to improve the ringindlelay 29, uponenergizing, attr-acts its armature-52 but, due to being weighted,armature 52`is'slow to pull up which controls'the length of the ringingperiod. Vhenfarma't'ure Y52 'finally' pulls up a circuit is closed forring cut-ott relay 30 by way of armature 50j and 'its grounded restingContact". *RelayY30,/upon energizing, closes a holding eircuittor` relayat armature 53; opens the signaling circuit at armature 56; andopens thecircuit of release relay 24 atfarmature`54. Releaserelay 24, upondeenergizing, closes a circuit for release magnet 35 by way of olfnormal spring 36 at armature42, 'whereupon said magnet energizes torestore the wiper-71 to normal position; vWhen they wiper 71 reachesnormal position, the shaft of the switch shifts the oli' normal springs3G and 37, whereupon the circuits of release magnet 35 and relay 27 areopened. Relay 27, upon deenergizing,opens the circuits of relays 29 and31, whereupon they deenergizef; and opens -the circuit of vibrator142,whereupon it discontinues its vibratory operation. y*Relay 31, upondeenergizing, removes direct ground 'lrom line conductor 21and switchesit through the double wound'line relay 23 to improve` transmission.y

Relay29, uponv deenergizing, opensthe circuit of relay 30,-whereuponsaid relay deenergizes to prepare the ringingeircuit; open the circuitof relay 32; and again close the cir cuit of relay 24 at armature 54.Relay 32, being slow to release, will hold up until relay 24 energizesto close a circuit for the former relay at arnjiature '40; a f f Vhenthe'subscriber at station'E responds Y to the ringing of his bell. byremoving his receiver, his telephone is connected across the y l commontalking line, whereby he and the callp nig subscriber A may now conversewith each other asidesired. c y f If the subscriber at station E doesnot respond to the `first ringing ot' hisbell', the sub scribe-ratstation A may ring it a. second time, or as 'many times as he desires,byre-r dia-lling thenumb'er, with his receiver olf, as in the firstinstance: when the samev opera-- tion takes place as already described.At the end otv theensuing conversation, both sub-1v scribers yreplacetheir receivers, whereupon line relay 23v deenergizes and opens thecircuit o release rel y 24 at larmature 39. Relay 24,upon dee'nergizing,opens the circuit of startrelay 32 at armature 40, whereupon rsaid relaydeenergizes to stop the motor genpower equipment P will be given now.Then start relay 32 of the connector H energizes,

a4 locking circuityfor itself is closed atarma- A ture 59 which may betraced from ground, resting'contact and armature 144,conductor G9,armature 59 and its working contact, and relay 32 to battery and acircuit 'for the mo-` tor generator set yis closed at armature 58` whichmay be traccdrom the commercial current source, conductor 131, themotor, conductor 64, Working'contact and armature 58, conductor.62,`conductor 96,` and vconductor 132 to the. other-side ofthecommercial curllO rent source. The motor=generator set is starte'dtooperate and builds up until the generator reaches an E. M. Fol 30 volts0r slightly over, whereupon relay lrllrenergizes over a" circuitincluding its top winding and resist-v ance 1li'. Relay 141, uponenergizing, opens the locking circuit of start relay 32 at armaturel-,which serves to, preventl while closed a rapid flashing et theswitchhook from opening the motor circuit be'liore it developssui/iicient speed; and co'iinectslthek generator in.'

parallel with battery B at armature 14.5. lillhen this latter circuit isclosed the generatoi` takes over the entire load of the switchboard andserves to reverse the current through the dry-cells and prolong theirlife. The twenty dry-cell battery B et approximately 30' Yvolts, servesto furnish current for the switchboard during the building` up of thegenerator and l'ills generator noise. y

As a further result ot the energization of start relay 32 a circuit isclosedfor busy lamp L at armature which may be trac-ed from thecommercial current source, conductor 131, conductor 97, busy lamp L,conductor 7G, armature 75 and its working contact, conductor ('32,conductor 9G, and conductor 132 to the other side of the commercialcurrent source. The lamp L lights over the above traced circuit andremains lighted as long as a receiver is oil the switchhook. may bemounted on the ceiling or in some other conspicuous place to serve as abusyv signal toiI the stations on the common line;

`When start relay 32 ot' the connector H deenergizes, the circuits otthe busy lamp L and the motor generator set are opened, whereupon thebusy signal is extinguished and the generator dies down. Nhen thegenerator gets below the current output of the battery B the current isreversed in the lower windingof relay 141, which now opposes thecurrent` in the upper winding and causes the relay to deenergize, thusacting as a circuit breaker and restoring the switchboard current supplyequipment to normal condition. Then armature 48 of relay 27`o'f thecon-v necter H is attracted, a circuit may be traced from grou ud andthe working contact of said armature, conductor 66, and vibrator 142 tobattery. The vibrator 142, upon energizing, attracts the pendulum 146and upon its inward swing the reed engages a contact which shortcircuits the winding of the vibrator, whereupon said vibratordeenergizes and allows the pendulum to swing outward again and close anenergizing circuit for the impedance coil 143. ,The impedance coilenergizes and the condenser bridged across its winding y stores. upcurrent so that an inductive kick is sent out over the signaling circuitto operate a biased bell, when the above energizing circuit ot impedancecoilylt is opened. The alter-v nate operation ot the vibrator andimpedance coil produces the desired signaling current.y

It will be assumed now that one of the subscribers on the common line,whose telephone is A, wishes to converse with the subscriber,

The lanip whose telephone is E,^but is unable to raise him by callinghis regular `telephone number 25 as described hereinbei'ore. Hetherefore decides to rcall him by 'means of his code ninn-` ber, which.is 05, it beingvfurther assumed that Vthe line is, idle when the callisoriginated.

In order to do this, the party at telephone A reinoveshis receiver andthen dials the code call number of the partyat telephone E. f

lWhen the receiver is removed at telephone il, the linerelay 2,3,release relay 251, and startingv relay 32 of connector H energize in thehereinbefore described manner to prepare the connector switch foroperation, light the busy lamp, and starttlie motor-generator setoperating-` f, l y ylVhen the calling party at telephone A operateSliiscalling device in accordance with the first digit O of the code number,the con# nector H operates in the hereinbefore described'nianner toraisethe wiper 71 opposite the tenth level ol bank contacts. As the wiperreaches the tenth level,tl1e shaft of the switch strikes the spring 38and closet-i` a circuit Ytor rel,aye2l8,.whieh relayenergizes todisconnect the wiper 7l vtroni the source of signaling currentandconnect it toi ground at armature 5l and to prepare a starting circuitfor` code call machine C@ at armature 4-9.

vtheir the calling party operates his calling device .in accordance withthe second and last digit, 5, of the code number, the connector Hoperates in the hereinl'iet'ore described manner to rotate the wiper .71in to the fifth contact, or the one indicated-as 73, thereby placingground on the sixthand eighteenth contact of the lefthand bank of thecode call machine CC lby way ot conductor '74. The relay 27'energizesand locks upas be'l'ore to start and hold the `vibrator 1412 inoperation, which, however, vperforms no usejtul function at this time;to prepare circuits tor relays 29 and 31; and to furtherprepare thestarting circuittor` code call machine CC. llhen the relayi26 iinallydeenergi zes,icircui ts are closed as before for relays v29 and 31,whereupon they energize, but they perform no useful function at thistinie Relay 3() is prevented romfoperating at this time4 due to theoperation otrelay 28.v

Y As a further: result of the deenergization oit' relay 26 arcircuit isclosed for slow vacting relay 82 oit' the code call machine @Catarmature 44;, which maybe traced from grounded armature4t and itsresting contact, arma-ture 46 and' its working contact,}armature 55 andits resting contact, working contact and armature 49,'conductor 63,wiper 87, armature 90 and its resting Contact, to relay 82 and bat tery.s Relay 82, upon energizing', closes a circuit for slow acting relay 83at armature 92, whereupon said relay energizes and 'closes a circuit formotor4 magnet, 85 at armature 93. Motor magnet 85, upon energizing,opens the circuit of relay 82at armature 90, whereupon said relayrdeenergizes and opens the circuit of relay Relay\83upon deenergizing,opens the circuit of motor magnet 85, whereupon said nia-guetdeenergizesand causes the wipers and 87 to take one. step tothe lirst contacts `intheir. respective ban rs. l/Vhen the Wiper 86 reaches the iirst contacta circuit is closed for relays 80 and 81 in series, whereupon they bothenergize and become locked up by way olf armature 89 oi' the latter. Asa further result of the energization ot vrelay 81, a circuit is preparedfor .double coil mag net 84 atarmature 88. Vtlhen theA wiper 87 reachesthe lirst contact, it encounters ground, whereupon the relay S2 againenergizes,v this time closing a circuit lor double coil magnet 84 atarmature 91, in addition to closing the circuit tor relay 83. lllagnet84, upon-energizing, closes a circuit for the code call bells 98, 99,etc., at armature94, which may be traced 'from the connnereial current,conductor-131, conductor 97, working contacts of armature 94, conductor95, through the bells 98, 99, etc., conductor 96, conductor 132, to thecommercial current.k AThe bells 98, 99, etc., ring` continuouslyuntiltheir circuit is broken by armature 94 falling,` away, which it doeswhen magnet 84 deenergizes as a result of its circuit beii'ig` opened atarmature 91 when relay'SQ again deenergizes.

As a result of the alternate energization and deenergization of relays82, 83 and inagnetS due to all contacts but the last ot the right handbanlrbeing grounded, the wipers 86 and 87` are rotated step by step,andthe code call bells are given a ring upon each step. vWhen, however,the wiper' 86 reaches the sixth contact, which contact was grounded bythe connector H, relay 81 is shorteircuited, whereupon it deenergizes toopen the circuit of relay 80 at armature 89; and to open `the energizingcircuit oit magnet S4 at armature 88. The wipers 86 and 87 continuetheir stepby-step rotation under control ofthe relays 82, 83 and magnet85, but the code call bells cannot ring' due to the operating circuit otma O'net 84 beingopen at armature S8. From n "'b this it will be seenthat the code rcall bells are given live rings, which is the codecallassigned to the subscriber E.

lVhen the wiper 8G reaches the thirteenth Contact, relays 80 and 81. areagain energized in series, whereupon the code call bells are again runera series of lire times, as the switch continues its step by stepmovement. lV'hen the eighteenth contact is reached rthe ringing` isagain cut oil' in preciselythe same manner as already explained. Thewipers continue to rotate, but without effect until wiper 86 reaches thetwentydourth or next `troni last contact, when a Circuit isclosed :torrelay 30 which may be traced from ground, relay 81, wiper 86, conductor61, working contact and armature 50, armature 52 and its working;Ycontact, and relay 30 to battery.

Relay 81 will not energize in series with relay 30, due to the highresistance of the latter. 'lelay 30, upon energizing, closes a holdingcircuit for relay at armaturer 53; opens the original energizing circuitof relay 82 at armature and opens the circuit oit' release relay 24 atarmature 54. Release relay 24, upon. deencrgizing, closes the circuit ofre lease magnet 35, whereupon the shait of the switch ,carryingv thewiper 714 is restored` to normal position as previously explained. Theshalt, in restoring, opensthe olf normal springsl, STand. 3S in the wellknown inanner,whereupon relays 27 and 28 dcenergize; thusdisconnecting,r the vibrator 142 and changing` the' connector H totalking;- condition as also previously explained. `VVhenthe wipers 8Gand 87 rotate to the twenty-lifth or last contact of the banks,` wiper87 no'longer l'inds ground,whereupon relay 82 is prevented fromenergizingl and the machine CCv comes to rest in what may be called homeposition, and is ready l'or use over again. y

Then the called` subscriber hears his code number sounded, he proceedsto the nearest telephone on the common line and by removing thereceiver, whereupon his telephone is connected across the talking line,he and the calling' subscriber A` mayy now converse with each other asbefore If, however, the called subscriber does not respond to the lirstdouble ringingof his code number, the subscriber at station A may causethe double ringinga second time, or as many times as he desires, by

re-diallinp; the number with his receiver oli',

as in the lirst instance; when the saine operation takes nlaceas alreadydescribed.

At the end of the ensuing;r conversation both subscribers' replace theirreceivers, whereupon the connector H andy power equipment P arerestoredto normal asalready explained and they, kas well ,as the connnonline, .are ready tor use again.' y i An explanation will now be givenofthe direct line system, vand for this purpose it will be assumed thatthe subscriber at station A desires to call the subscriber at station Ewithout using the common talking' line. order to do this, the subscriberat station il merely reinoveshis receiver, whereuponthe line and batteryfeed relays 104 and 105 of the llO In f

116. Relay 107, upon energizing, locks up to ground on the back contactot the circuit breaker 14:1 at armature 121, by way of the restingcontact `and armature 60, and closes a circuit for the motor-generatorset at armature 122, whereupon the motor generator' set starts operatingas has been already ein plained. Ielay 1041, upon energizing, preparesthe talking circuit at armatures 112 and 115; and disconnects the lineconductors 123 and 124L from line relay 103 at armatures 113 and 114,respectively, and further prepares the talking circuit as well asconnects up the ringing circuit which may be traced from ground, lowerwinding of ring'cut-oii relay 100, resting Contact and armature 120,working contact and armature 114, line conductor 12st, condenser andbell bridged across the line atsubstation E', line conductor 123,armature 113 and its working contact, armature 113 and its restingcontact, and impedance coil 143 with the condenser in bridge of itswinding to battery. rI`he biased bell at the called subscriberstelephone E continues ringing over the above traced circuit as long `asthe calling subscriber A holds his receiver oliq the switchhook, thelatter receiving a ringing tone by way of condenser 125.

IVhen the subscriber at station E responds to the actuation ot' his bellby removing his receiver, a direct current bridge is placed across theline, whereupon the ring cut-oit relay 106 energizes and locks up toground at working contact and armature 117, by way of armature 119 andits working contact, and at the same time opens the circuit of thevibrator to discontinue its operation. As a 'further result of theenergization of relay 106, the signaling circuit is broken and thetalking circuit established at armatures 118 and 120, the latter circuitbeing shown by the heavy conductors. The subscribers may now conversewith each other as desired.

At the end of the ensuing conversation, both subscribers replace theirreceivers. IlVhen the receiver at E is replaced, nothing happens, butwhen the receiver at A is replaced the direct current bridge is replacedby the condenser and bell, whereupon relays a and 105 deenergize. Relay10e/l, upon deenergizing, restores the line conductors to their originalcondition; while relay 105, upon deenergizing, opens the locking circuitof relay 10G, and opens the circuit of relay 107. Relay 10G, upondeenergizing, further opens the talking` circuit and prepares thesignaling circuit; while relay 107, upon deenergizing, opens the circuitof the motor-generator set, thus allowing it to restore to its normalinoperative condition. The direct line is now fully restored and readyfor use over again.

It the subscriber at the station E does not respond to the actuation ofhis bell, the subscriber at stat-ion A merely replaces his receiver,whereupon the lrelay group R is restored to norm al and .the powerequipment P is disconnected as has already been explained.

Should the subscriber E originate the call instead ot the subscriber A',practically the same operations will take place as described when A.originated the call. In fact, the only difference lies in the tact thatline relay 103 energizes instead or line relay 104 to close thesignaling circuit and prepare the talking circuit.

Having described my invention, what I consider tobe new and desire tohave protected by Letters lBatent will be pointed out in the appendedclaims.

Vilhat is claimed is:

1. In a telephone system, the combination with a common talking,selective signaling Vsystem providing with a line having a plurality oisubscribers stations thereon, of a direct line system accessible to twosubscribers ot said common line, a source of signaling current,automatic means controlled over said common line for signaling withAsaid current any subscriber thereon individually, automatic meansresponsive to the lifting of a receiver on said direct line forsignaling with said current the other subscriber thereon, and automaticmeans responsive to the lifting of said other subscribers receiver forstopping said signaling and connecting up said subscribers for talking.

2. A telephone system comprising two stations normally disconnected, acentral source of talking current, a central source of signalingcurrent, means responsive to the removal or' the receiver at eitherstation for connecting said signaling' current source to the line of theother station, and means for cutting ofi' said signaling source and forclosing the talk ing circuit when the receiver is removed at the stationcalled.

3. In a telephone system, a plurality of stations, a common conductorconnected to said stations for supplying talking and sig naling currentsto said stations, a retard coil, and Ameans whereby said coil isincluded in circuit-.with said conductor while the saine is used forsupplying talking current but not while it is used for supplyingsignaling current.

4. In a telephone system, a plurality oit stations, a common conductorconnected to said stations ior supplying talking and signaling currentsrto said stations, a retard coil normally in circuit with said conductor,and means for open circuiting said coil while the conductor is in usefor supplying signaling current.

5. In a telephone system comprising a party line, said line terminatingin an automatic switch, individual signaling conductors terminating inAa portion oi the bank of said switch and extending to the severalstations on said line, a code call machine, and con ductors forcontrolling said machine terminating in another portion of the bank ofsaid switch. i G. In a code call system, al code ringing machine, adirective switch for selecting a code and for starting said ringingmachine, and means responsive to the generation oitwo successive codesignals for releasing said switch and for stopping the ringing machine.7. In a telephone system comprising a. single line having a plurality ofstations thereon, a central source of talking cuirent comprising a motorgenerator, means for starting said motor generator whenever any stationuses the line, and a single signal actuated while the motor is runningand serving as a busy signal to said stations.

8. In a telephone system, a plurality of sta tions, an electricgenerator, means operated responsive to the initiation of al call fromany station to start the generator and responsive to the termination ofthe call to stop it, and means for rendering the stopping meansineffective while the generator voltage is below y a predeterminedvoltage.

9. In a telephone system, a plurality of sta-V tions, an electricgenerator, an electric motor for driving the same, means operatedresponsive to the initiation of a call 'from any station to start themotor and responsive to the terminationot` the calls to stop the motor,and means Jfor preventing the stopping of the motor before the generatorreaches a predetermined voltage.

10. In a telephone system, a plurality of stations, a generator, meansoperated responsive to the initiation of a call to start the generator,means for maintaining the generator in operation, and means operatedwhen the generator reaches a predetermined voltage to render theoperation of the last named means dependent upon the continuation of acall.

11. In a telephone system, a plurality of stations, a source ofelectromotive force including a battery and a generator, means Yforoperating the generator, means for connecting the `generator in parallelwith the battery when the generator electromotive force becomes slightlygreater than the battery electi'oinotive force, means operated from thebattery responsive to the initiation of a call to cause the first namedmeans to operate, and operated responsive to the cessation ot a call tocause the first named means to stop the generator il:A the second namedmeans has operated.

12. In a telephone system, a station, a switch having a plurality ofcontacts, means whereby said station may automatically operate theswitch to select a desired Contact, a code call machine associated withsaid contacts, means for automatically operating the code call machineresponsive to the selection of a contact, said machine including meansfor repeatedly sending out a code corresponding to the contact selected,and means for automatically stopping the code call machine after thecode has been sent out a predetermined number of times.

13. In a telephone system, a plurality oil stations each having ringingmeans, a switch having a number of contacts each of which is associatedwith the ringing means of a dit- `ferent station, vadditional contactson the 'stations on a party line, each stationhaving ringing means, anautomatic switch accessible to all of said stations, a code callmachine, means for operating said switch from any of said stations toindividually signal any other station or to operate the code callmachine, common signalling means, and means effective if the code callmachine is selected for transmitting one of a plurality of Vcode signalsto the common signalling means,

the particular code transmitted being determined by the particularsetting of the switch.

15. In a telephone system, a plurality of stations on a party line eachstation having ringing means, a switcn having two groups of contactseach of the contacts oi one ot the groups being associated with theringing means of a different rone ot the stations, a code call machine.associated with the contacts of the second group, means whereby theswitch may be operated from any station to select any contact` meansresponsive to the selection of a contact in the lirst mentioned group:tor operating the ringing means of the particular station associatedwith the selected contact, a common signalling apparatus, and meansresponsive to the selection ot' any contact in the second group 'foroperating the code call machine 'for t 'ansmitting a particular one of aplurality of codes to the signalling apparatus, the particular codebeing determined by the particular contact selected.

In witness whereof, I hereunto subscribe my name this 6th dav of May. A.D., 1925.

i' CLARENCE E. LOMAX.

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